TOKYO — Japan’s government said yesterday that it would step in and take “firm measures” to tackle contaminated water leaks at the country’s crippled nuclear plant, including possibly funding a multi-billion-dollar project to fix the problem.

Calling water containment at the stricken Fukushima Daiichi plant an “urgent issue”, Prime Minister Shinzo Abe ordered the government for the first time to get involved to help the struggling plant operator, Tokyo Electric Power Company (Tepco), handle the crisis.

“There is heightened concern among the public, particularly about the contaminated water problem,’’ Mr Abe said yesterday during a government nuclear disaster response meeting at his office. “This is an urgent matter that needs to be addressed. The government will step in to take firm measures.”

The announcement came a day after Tepco said some of the water was seeping over, or around, an underground barrier it created after injecting chemicals into the soil that solidified into a wall.

The latest problem involves underground water that has built up over the last month since Tepco began creating the chemical walls underground to stop leaks, after detecting radiation spikes in water samples in May.

“We think that the volume of water (leaking into the Pacific) is about 300 tonnes a day,” said Mr Yushi Yoneyama, an official with the Ministry of Economy, Trade and Industry, which oversees energy policy.

Since a major leak via a maintenance pit a month after three Fukushima reactors went into meltdown following the 2011 earthquake and tsunami, Tepco had denied any further leaks into the sea until acknowledging them last month, despite repeated warnings by experts.

As early as January this year, Tepco found fish contaminated with high levels of radiation inside a port at the plant. Local fishermen and independent researchers had already suspected a leak of radioactive water, but Tepco denied the claims.

Environmental group Greenpeace said Tepco had “anxiously hid the leaks” and urged Japan to seek international expertise.

The underground barrier on the coastal embankment has somewhat slowed the leaks, but has caused underground water to swell at the complex. To prevent an overflow above the surface, which is feared to happen within weeks, Tepco will start pumping out about 100 tonnes of underground water from coastal observation wells by the end of this week.